Showing papers in "Pest Management Science in 2023"

Status of the biopesticide market and prospects for new bioherbicides.

Abstract: Biopesticides (commonly called Biocontrol or more recently bioprotection) have been experiencing double digit growth and now comprise about 10% of the global pesticide market driven by increased return on investment, restrictions on chemical pesticides, and pesticide resistance and residue management. However, despite the large need for new herbicides due to widespread and increasing resistance to herbicides with almost most of the chemical modes of action, bioherbicides are an insignificant percentage of the total. The technical difficulty in finding bioherbicides that can compete with the spectrum and price of chemical herbicides has left agriculture with a paucity of new bioherbicides. Billions of dollars of investment capital is being invested in new, innovative startups, but only a small number focus on bioherbicide discovery and development, due to the perceived higher risk than plant biotech, biostimulants, bionutrients and other categories of biopesticides. However, the exciting new technologies that these startups are developing such as RNAi, sterile pollen, and systemic metabolites have potential to impact the market in ten years or less. This article is protected by copyright. All rights reserved.

Spatiotemporal distancing of crops reduces pest pressure while maintaining conservation biocontrol in oilseed rape.

Abstract: BACKGROUND Agricultural landscapes provide resources for arthropod pests as well as their natural enemies. In order to develop integrated pest management (IPM) practices, it is important to understand how spatiotemporal location influences crop colonization and damage severity. We performed a three-year (2016-2018) field experiment in winter oilseed rape (OSR, Brassica napus) fields in Estonia, where half of the fields were within 500 m of the location of the previous year's winter oilseed rape field, and half outside this zone. We investigated how distance from the previous year's OSR crop influences the infestation and parasitism rates of two of its most important pests - the pollen beetle (Brassicogethes aeneus) and the cabbage seed weevil (Ceutorhynchus obstrictus). RESULTS When the distance from the previous year's OSR crop was > 500 m, we recorded significantly reduced pest pressure by both B. aeneus and C. obstrictus, in study fields. Biocontrol of both pests, provided by parasitic wasps, was high in each study year and commonly not affected by distance. Mean parasitism rates of B. aeneus were > 31%, occasionally reaching > 70%; for C. obstrictus, mean parasitism was > 46%, reaching up to 79%, thereby providing effective biocontrol for both pest species. CONCLUSION Spatiotemporal separation of OSR fields can reduce pest pressure without resulting in reduced parasitism of OSR pests. This supports a spatiotemporal field separation concept as an effective and sustainable technique for IPM in OSR. This article is protected by copyright. All rights reserved.

The Mythimna separata general odorant binding protein 2 (MsepGOBP2) is involved in the larval detection of the sex pheromone (Z)-11-hexadecenal.

Abstract: BACKGROUND Mythimna separata is a notorious pest causing crop damages at the larval stage. Gaining insight into larval olfaction mechanisms would provide knowledge for olfaction-based management of M. separata larvae. RESULTS In the present research, (Z)-11-hexadecenal (Z11-16: Ald), a major component of M. separata sex pheromone, was found to attract early-instar larvae of M. separata in a food context. Using a fluorescent binding assay, we found that M. separata general odorant binding protein 2 (MsepGOBP2) exhibited high binding affinity to Z11-16: Ald. Further, silencing of MsepGOBP2 resulted in a sharp reduction of the response to Z11-16: Ald, which could not be mitigated by increasing the concentration of Z11-16: Ald. Additionally, we employed molecular dynamics-based approaches to unravel the interaction details between MsepGOBP2 and Z11-16: Ald, specifically the binding of Z11-16: Ald to MsepGOBP2. CONCLUSION Z11-16: Ald is attractive to early-instar larvae of M. separata, and MsepGOBP2 is identified to be indispensable in the larval detection of Z11-16: Ald. These results could aid in the development of olfaction-based methods for controlling M. separata in the larval stage. This article is protected by copyright. All rights reserved.

Activation of CncC pathway is involved in the regulation of P450 genes responsible for clothianidin resistance in Bradysia odoriphaga.

Abstract: BACKGROUND Insect cytochrome P450 monooxygenases (P450s) play a key role in the detoxification metabolism of insecticides and their overexpression is often associated with insecticide resistance. Our previous research showed that the overexpression of four P450 genes is responsible for clothianidin resistance in B. odoriphaga. In this study, we characterized another P450 gene CYP6FV21 associated with clothianidin resistance. However, the molecular basis for the overexpression of P450 genes in clothianidin resistant strain remains obscure in B. odoriphaga. RESULTS In this study, the CYP6FV21 gene was significantly overexpressed in the clothianidin resistant (CL-R) strain. Clothianidin exposure significantly increased the expression level of CYP6FV21. Knockdown of CYP6FV21 significantly increased the susceptibility of B. odoriphaga larvae to clothianidin. The transcription factor Cap 'n' Collar isoform-C (CncC) was highly expressed in the midgut of larvae in B. odoriphaga. The expression level of CncC was higher in the CL-R strain compared with the susceptible (SS) strain. Clothianidin exposure caused reactive oxygen species (ROS) accumulation and significantly increased the expression level of CncC. Knockdown of CncC cause a significant decrease in the expression of CYP3828A1 and CYP6FV21 and P450 enzyme activity, and leads to a significant increase in mortality after exposure to LC30 clothianidin. After treatment with CncC agonist curcumin, the P450 activity and the expression levels of CYP3828A1 and CYP6FV21 significantly increased, and larval sensitivity to clothianidin decreased. The ROS scavenger NAC treatment significantly inhibited the expression levels of CncC, CYP3828A1 and CYP6FV21 in response to clothianidin exposure and increased larval sensitivity to clothianidin. CONCLUSION Taken together, these results indicate that activation of the CncC pathway by the ROS burst plays a critical role in clothianidin resistance by regulating the expression of CYP3828A1 and CYP6FV21 genes in B. odoriphaga. This study provides more insight into the mechanisms underlying B. odoriphaga larval resistance to clothianidin.

Spatiotemporal dynamics of fluopyram trunk-injection in Pinus massoniana and its efficacy against pine wilt disease.

Abstract: BACKGROUND Pine wilt disease (PWD) is a destructive disease of pine trees caused by the pinewood nematode, Bursaphelenchus xylophilus. Fluopyram, a novel nematicide compound with systemic activity, is a prospective trunk-injection agent against pinewood nematodes. The disadvantage of current trunk-injection agents is that they were not evenly distributed in tree tissues and were poor in the persistence of effect and efficiency. Therefore, we investigated the spatiotemporal transport pattern and residue behavior of fluopyram following its injection into the trunk of Pinus massoniana. RESULTS Fluopyram transport in the trunk occurred through radial diffusion and vertical uptake within one week of the injection, reaching all tissues of P. massoniana, including apical branches and needles. Three years after the field test, the infection of PWD declined substantially with treatment using fluopyram trunk-injection agent, which demonstrated 100% efficacy in both the mild and moderate occurrence areas and 71.1% efficacy in the severe occurrence area. Fluopyram trunk-injection agent exerted substantial control over PWD, with its efficacy being influence by the infection time of PWD. The half-life of 10% fluopyram in treated pine trees was 346.6 d with three-year persistence. CONCLUSION The advantages of uniform distribution and long persistence of fluopyram in the tree after injection made it has evident efficacy on pine wilt disease. Overrall, fluopyram trunk-injection has potential to prevent PWD. This article is protected by copyright. All rights reserved.

Resistance-driven innovations in the discovery of bactericides: novel triclosan derivatives decorating isopropanolamine moiety as promising anti-biofilm agents against destructive plant bacterial diseases.

Abstract: BACKGROUND Controlling bacterial infections in plants is a major challenge due to the appearance of resistant strains. As a physical barrier, the bacterial biofilm helps bacterial infections acquire drug resistance by enabling bacteria to accommodate complex and volatile environmental conditions and avoid bactericides' effects. Thus, developing new antibacterial agents with antibiofilm potency is imperative. RESULTS A series of simple triclosan derivatives containing isopropanolamine moiety were elaborately designed and assessed for antibacterial behavior. Bioassay results showed that some title compounds had excellent bioactivity against three destructive bacteria Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and Pseudomonas syringae pv. actinidiae (Psa). Notably, compound C8 displayed high bioactivities toward Xoo and Xac, the related EC50 values were 0.34 and 2.11 μg mL-1 , respectively. In vivo trials revealed that compound C8 exhibited excellent protective activities against rice bacterial blight and citrus bacterial canker at 200 μg mL-1 , with a control effectiveness of 49.57% and 85.60%, respectively. Compound A4 had remarkably inhibitory activity toward Psa, with an EC50 value of 2.63 μg mL-1 , and demonstrated outstanding protective activity with a value of 77.23% against Psa in vivo. Antibacterial mechanisms indicated that compound C8 dose-dependently prevented biofilm formation and extracellular polysaccharide production. C8 also significantly weakened the motility and pathogenicity of Xoo. CONCLUSION This study contributes to the development and excavation of novel bactericidal candidates with broad-spectrum antibacterial activity by targeting bacterial biofilm to control refractory plant bacterial diseases. This article is protected by copyright. All rights reserved.

Effects of far-red light on tritrophic interactions between the two-spotted spider mite (Tetranychus urticae) and the predatory mite Phytoseiulus persimilis on tomato.

Abstract: BACKGROUND The use of LED lights in horticulture allows growers to adjust the light spectrum to optimize crop production and quality. However, changes in light quality can also influence plant-arthropod interactions, with possible consequences for pest management. The addition of far-red light has been shown to interfere with plant immunity, thereby increasing plant susceptibility to biotic stress and increasing pest performance. Far-red light also influences plant emission of volatile organic compounds (VOCs) and might thus influence tritrophic interactions with biological control agents. We investigated how far-red light influences the VOC-mediated attraction of the predatory mite Phytoseiulus persimilis to tomato plants infested with Tetranychus urticae, and its ability to control T. urticae populations. RESULTS Far-red light significantly influences herbivore-induced VOC emissions of tomato plants, characterized by a change in relative abundance of terpenoids, but this did not influence the attraction of P. persimilis to herbivore-induced plants. Supplemental far-red light led to an increased population growth of T. urticae and increased numbers of P. persimilis. This resulted in a stronger suppression of T. urticae populations under supplemental far-red light, to similar T. urticae numbers as in control conditions without supplemental far-red light. CONCLUSION We conclude that supplemental far-red light can change herbivore-induced VOC emissions but does not interfere with the attraction of the predator P. persimilis. Moreover, far-red light stimulates biological control of spider mites in greenhouse tomatoes due to increased population build-up of the biocontrol agent. This article is protected by copyright. All rights reserved.

Factors influencing short term parasitoid establishment and efficacy for the biological control of Halyomorpha halys with the samurai wasp Trissolcus japonicus.

Abstract: BACKGROUND Classical biological control has been identified as the most promising approach to limit the impact of the invasive pest species Halyomorpha halys (Heteroptera: Pentatomidae). This study investigated the parasitism rate at sites where the biocontrol agent Trissolcus japonicus (Hymenoptera: Scelionidae) was released and where its unintentional introduction took place, in the Trentino-South Tyrol region. The effect of land use composition was studied to understand which factors favor the establishment of hosts and parasitoids, including native and exotic species. RESULTS The released T. japonicus were detected a year after the start of the program, with a significant parasitoid impact and discovery, compared to control sites. Trissolcus japonicus was the most abundant H. halys parasitoid, Trissolcus mitsukurii and Anastatus bifasciatus were recorded as well. The efficacy of T. mitsukurii was lower in sites where T. japonicus was successfully established, suggesting a possible competitive interaction. Parasitism level by T. japonicus at the release sites was 12.5% in 2020 and 16.4% in 2021. The combined effect of predation and parasitization increased H. halys mortality up to 50% at the release sites. Landscape composition analysis showed that both H. halys and T. japonicus were more likely found at sites with lower altitude and with permanent crops, while other hosts and parasitoids preferred different conditions. CONCLUSION Trissolcus japonicus showed a promising impact on H. halys, at release and adventive sites, with minor non-target effects, mediated by landscape heterogeneity. The prevalence of T. japonicus in landscapes with permanent crops could support IPM in the future. This article is protected by copyright. All rights reserved.

Nonanal, a new fall armyworm sex pheromone component, significantly increases the efficacy of pheromone lures.

Abstract: BACKGROUND The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a global pest that feeds on more than 350 plant species and severely limits production of cultivated grasses, vegetable crops and cotton. An efficient way to detect new invasions at early stages and monitor and quantify the status of established infestations of this pest is to deploy traps baited with species-specific synthetic sex pheromone lures. RESULTS We reexamined the compounds in the sex pheromone glands of FAW females by GC-EAD, GC-MS, behavioral, and field assays. A new bioactive compound from pheromone gland extracts was detected in low amounts (1% relative to (Z)-9-tetradecenyl acetate (Z9-14:OAc), the main pheromone component) and identified as nonanal. This aldehyde significantly increased attraction of male moths to a mix of Z9-14:OAc and (Z)-7-dodecenyl acetate in olfactometer assays. Adding nonanal to this 2-component mix also doubled male trap catches relative to the 2-component mix alone in cotton fields, whereas nonanal alone did not attract any moths. The addition of nonanal to each of three commercial pheromone lures also increased male catches by 53-135% in sorghum and cotton fields. CONCLUSION The addition of nonanal to pheromone lures should improve surveillance, monitoring and control of FAW populations. This article is protected by copyright. All rights reserved.

Transcriptome analysis indicates the involvement of herbicide-responsive and plant-pathogen interaction pathways in the development of resistance to ACCase inhibitors in Apera spica-venti.

Abstract: BACKGROUND The continuous use of the herbicides contributes to the emergence of the resistant populations of numerous weed species that are tolerant to multiple herbicides with different modes of action (multiple resistance) which is provided by non-target-site resistance mechanisms. In this study, we addressed the question of rapid acquisition of herbicide resistance to pinoxaden (acetyl CoA carboxylase inhibitor) in Apera spica-venti, which endangers winter cereal crops and has high adaptation capabilities to inhabit many rural locations. To this end, de novo transcriptome of A. spica-venti was assembled and RNA-seq analysis of plants resistant and susceptible to pinoxaden treated with this herbicide was performed. RESULTS The obtained data showed that the prime candidate genes responsible for herbicide resistance were those encoding 3-ketoacyl-CoA synthase 12-like, UDP-glycosyltransferases (UGT) including UGT75K6, UGT75E2, UGT83A1-like, and glutathione S-transferases (GSTs) such as GSTU6 and GSTU1. Also, such highly accelerated herbicide resistance emergence may result from the enhanced constitutive expression of a wide range of genes involved in detoxification already before herbicide treatment and may also influence response to biotic stresses, which was assumed by the detection of expression changes in genes encoding defence-related proteins, including receptor kinase-like XA21. Moreover, alterations in the expression of genes associated with methylation in non-treated herbicide-resistant populations were identified. CONCLUSION The obtained results indicated genes that may be involved in herbicide resistance. Moreover, they provide valuable insight into the possible effect of resistance on the weed interaction with the other stresses by indicating pathways associated with both abiotic and biotic stresses.

Economic and financial model to the mass-rearing of Macrolophus pygmaeus (Rambur) (Heteroptera: Miridae), a biological control agent against the tomato moth Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in protected culture.

Abstract: BACKGROUND Tuta absoluta (Meyrick) is a major pest of tomato produced in greenhouses and open field, causing severe damages to crops, reducing the quality of tomato fruits. The current maintenance of the pest populations below the economic threshold is not achieved by natural and classical control, thus requiring the continuous application of biological control agents (BCA), under an augmentative or inoculative approach. The present study aims to develop an economic and financial model to evaluate the commercial viability of a continuous mass production of Macrolophus pygmaeus (Rambur), a BCA commonly used against the tomato moth, T. absoluta, in protected culture. The estimations for our model were based on two approaches: the farm-level impact analysis and the benefit-cost analysis. RESULTS The results of the farm-level analysis show that the adoption of a more sustainable biological control (BC) approach is profitable for farmers and the benefit-cost analysis provides evidence that the investment on a new factory dedicated to the mass rearing of M. pygmaeus to control tomato moth populations generates a positive Net Present Value (NPV) of 7.2 million euros, corresponding to an Internal Rate of Return (IRR) of 28.4% per year. CONCLUSION Our results are in line with i) the more recent European Commission proposals for a new Regulation on sustainable use of plant protection products, which includes the reduction of 50% the use and risk of chemical pesticides by 2030 and ii) most of the existing literature when concluding that new projects on BCA production are worth for investments. This article is protected by copyright. All rights reserved.

Systemic enantioselectivity study of penthiopyrad: enantioselective bioactivity, acute toxicity, degradation and influence on tomato.

Abstract: BACKGROUND In order to promote the green development of agriculture, it is important to study the enantioselective effect of chiral pesticides. The bioactivity of the chiral fungicide penthiopyrad (PEN) racemate and enantiomers against phytopathogens, toxicity to non-target organisms, effect on tomato fruit growth and maturation, and environmental fate in tomato cultivation were evaluated at enantioselective level in this study. RESULTS The results indicated that at the same efficacy, the optically pure S-(+)-PEN could lower the dosage of racemate by 20%-96%. The S-enantiomer had low toxicity to earthworms. Besides, the S-(+)-PEN did not cause significant abiotic stress to the tomato and increased fruit fresh weight and size via modulating the contents of plant hormones. However, the content of H2 O2 , O2 - and malondialdehyde in the R-enantiomer treatment group was significantly higher than the control group. The effect of the racemate on tomato fruit was between the enantiomers. Furthermore, compared to R-(-)-PEN and racemate, the S-enantiomer degraded more quickly in tomato fruit, leaves, and soil, reducing the danger of human exposure. CONCLUSION The S-enantiomer is highly effective and less toxic. The development of enantiomer pure S-(+)-PEN products might be an efficient and low-risk strategy. The results lay the foundation for comprehensive evaluation and proper application of the PEN. This article is protected by copyright. All rights reserved.

Efficiency of inorganic fungicides against the formation of Erysiphe necator chasmothecia in vineyards.

Abstract: BACKGROUND A reduction in chasmothecia, as important inoculum of grape powdery mildew (Erysiphe necator Schwein.) is essential for disease control in vineyards; the use of fungicides during the formation of chasmothecia on vine leaves, late in the growing season, may accomplish this. Inorganic fungicides, such as sulphur, copper, and potassium bicarbonate, are very useful for this purpose because of their multi-site mode of action. The aim of this study was to evaluate chasmothecia reduction using different fungicide applications late in the growing season in commercially managed vineyards and in an exact application trial. RESULTS Chasmothecia on vine leaves were reduced in commercial vineyards by four copper (P = 0.01) and five potassium bicarbonate (P = 0.026) applications. The positive effect of potassium bicarbonate was also confirmed in the application trial, where two applications showed lower chasmothecia numbers than the control (P = 0.002). CONCLUSION The application of inorganic fungicides reduced the amount of chasmothecia as the primary inoculum source. Potassium bicarbonate and copper are of further interest for disease control, as these fungicides can be used by organic and conventional wine growers. The application of these fungicides should be carried out as late as possible before harvest to reduce chasmothecia formation and, consequently, the potential for powdery mildew infestation in the subsequent season.

Effectiveness of field-exposed attract-and-kill devices against the adults of Popillia japonica (Coleoptera: Scarabaeidae): a study on duration, form and storage.

Abstract: BACKGROUND The Japanese beetle Popillia japonica Newman is an insect pest native to Japan that has spread into North America, the Azores, and, recently, into continental Europe. Here, we present a study assessing the effectiveness of a Long-Lasting Insecticide-treated Net (LLIN), assembled in semiochemical-baited attract-and-kill devices (A&Ks) as a low environmental impact means to control P. japonica in the field. We compared the attractiveness of three different forms of A&Ks that were left outdoors throughout the summer, and the residence time of P. japonica landing on them. Moreover, we performed a preliminary study testing the effectiveness of new LLINs after storage. Collected data also allowed us to investigate the beetles' diel flight patterns in relation to meteorological conditions. RESULTS Killing effectiveness of the field-exposed A&Ks declined steadily over the flight season (from 100% to 37.5%) associated with a decrease in residues of α-cypermethrin, the active ingredient in the LLINs. The different A&K forms (pyramidal, octahedral, and ellipsoidal) attracted similar numbers of beetles. Individual beetles' residence time ranged from 75-95 s and differed slightly between A&K forms. Effectiveness of LLINs decreased by about 30% after one year storage. Based on numbers landing on A&Ks, the beetles' flight activity peaked about 2:30 p.m. and was inversely correlated with relative humidity. CONCLUSION This study indicates that semiochemical-baited A&Ks are effective for controlling P. japonica in the field. Because of active ingredient decay the LLINs should be replaced after 30-40 days of field exposure to ensure that the A&Ks remain fully functional. This article is protected by copyright. All rights reserved.

Overexpression of a beta-1,6-glucanase gene GluM in transgenic rice confers high resistance to rice blast, sheath blight and false smut.

Abstract: BACKGROUND Frequent fungal diseases tend to cause severe loss in rice production. As a main component of fungal cell wall, glucan plays an important role in the growth and development of fungi. Glucanase can inhibit the growth of fungi by breaking the glycosidic bond, which may be a promising target for developing rice varieties with broad-spectrum disease resistance. RESULTS We transferred a codon-optimized β-1,6-glucanase gene (GluM) from myxobacteria into the japonica rice variety ZH11, and obtained a large number of individual transgenic plants with GluM overexpression. Based on molecular analysis, three single-copy homozygous lines with GluM overexpression were selected for assessment of fungal disease resistance at the T3 generation. Compared with that of recipient cultivar ZH11, the area of rice blast lesion in transgenic rice was reduced by 82.71%; that of sheath blight lesion was decreased by 35.76%-43.67%; the sheath blight resistance in the field was enhanced by an average of 0.75 grade over three years; and the incidence of diseased panicles due to rice false smut was decreased by 65.79%. More importantly, there was no obvious loss in yield (without significant effect on agronomic traits). Furthermore, the plants overexpressing a β-1,6-glucanase gene showed higher disease resistance than the rice plants overexpressing a β-1,3-glucanase gene derived from tobacco. CONCLUSION The β-1,6-glucanase gene GluM can confer broad-spectrum disease resistance to rice, providing an environment-friendly alternative way to effectively manage fungal pathogens in rice production. This article is protected by copyright. All rights reserved.

Structural characterization, derivatization and antibacterial activity of secondary metabolites produced by termite-associated Streptomyces showdoensis BYF17.

Abstract: BACKGROUND Insect-associated Streptomyces is a valuable resource for development of compounds with antibacterial potential. However, relatively little is known of the secondary metabolites produced by termite-associated Streptomyces. RESULTS Here, seven compounds including o-acetaminophenol (1), phenazine-1,6-dicarboxylic acid (2), phenylacetic acid (3), phenazinolin D (4), izumiphenazine A (5), izumiphenazine B (6) and phenazinolin E (7) were obtained from the fermentation broth of a termite-associated Streptomyces showdoensis BYF17, which was isolated from the body surfaces of Odontotermes formosanus. Two additional novel derivative compounds (6a and 6b) were synthesized via acetylation and methylation, respectively. The structures of these compounds were elucidated by spectroscopic analyses. The antibacterial bioassay showed that compound 6a displayed strong inhibitory effects against Pseudomonas syringae pv. actinidiae (Psa), with the diameter of inhibition zone (ZOI) value of 20.6 mm, which was comparable to that of positive gentamicin sulfate with the ZOI value of 25.6 mm. Furthermore, the 5th-day curative activities of both compounds 6 and 6a against kiwifruit bacterial canker were 71.5%, which were higher than those of referred oxine-copper (55.0%) and ethylicin (46.8%) at the concentration of 200 μg/mL. In addition, the mechanism analysis based on a scanning electron microscope revealed that both compounds 6 and 6a destroyed the integrity of the Psa cells membrane. CONCLUSION The results of biological tests showed that these bioactive compounds exhibit potent antimicrobial activities, which have the potential to be developed into new antibacterial agents. This article is protected by copyright. All rights reserved.

The mechanism of Cry41-related toxin against Myzus persicae based on its interaction with Buchnera-derived ATP-dependent-6-phosphofructokinase.

Abstract: BACKGROUND Myzus persicae (Hemiptera: Aphididae) is one of the most notorious pests to many crops worldwide. Most Cry toxins produced by Bacillus thuringiensis show very low toxicity to M. persicae; however, a study showed that Cry41-related toxin had moderate toxic activity against M. persicae. In our previous work, potential Cry41-related toxin binding proteins in M. persicae were identified, including Cathepsin B, calcium-transporting ATPase, and Buchnera-derived ATP-dependent-6-phosphofructokinase (PFKA). Buchnera is an endosymbiont present in almost all aphids and it provides necessary nutrients for aphid's growth. This study investigated the role of Buchnera-derived PFKA in Cry41-related toxicity against M. persicae. RESULTS In this study, recombinant PFKA was expressed and purified, and in vitro assays revealed that PFKA bound to Cry41-related toxin, and Cry41-related toxin at 25 μg/mL significantly inhibited the activity of PFKA. Additionally, when M. persicae was treated with 30 μg/mL of Cry41-related toxin for 24 h, the expression of dnak, a single-copy gene in Buchnera, was significantly decreased, indicating a decrease in the number of Buchnera. CONCLUSION Our results suggest that Cry41-related toxin interacts with Buchnera-derived PFKA to inhibit its enzymatic activity and likely impair cell viability, resulting in a decrease in the number of Buchnera, and finally leading to M. persicae death. These findings open new perspectives in understanding the mode of action of Cry toxins and are useful to help improve the Cry toxicity for aphid control. This article is protected by copyright. All rights reserved.

Hormesis effects in tomato plant growth and photosynthesis due to acephate exposure based on physiology and transcriptomic analysis.

Abstract: BACKGROUND Hormesis is a common phenomenon in toxicology described as low-dose stimulation due to a toxin which causes inhibition at a high dose. Pesticide hormesis in plants has attracted considerable research interest in recent years; however, the specific mechanism has not yet been clarified. Acephate is an organophosphorus insecticide that is used worldwide. Here, hormesis in tomato (Solanum lycopersicum L.) plant growth and photosynthesis after acephate exposure is confirmed, as stimulation occurred at low stress levels whereas inhibition occurred after exposure to high concentrations. RESULTS We found that low acephate concentration (5-fold lower than recommended application dosage) could enhance chlorophyll biosynthesis and stimulate photosynthesis effects, and thus improve S. lycopersicum growth. A high level of acephate (5-fold higher than recommended application dosage) stress inhibited chlorophyll accumulation, decreased photosystem II efficiency and blocked antioxidant reactions in leaves, increasing reactive oxygen species levels and damaging plant growth. Transcriptomic analysis and quantitative real-time PCR results revealed that the photosynthesis - antenna proteins pathway played a crucial role in the hormesis effect, and that LHCB7 as well as LHCP from the pathway were the most sensitive to acephate hormesis. CONCLUSION Our results showed that acephate could induce hormesis in tomato plant growth and photosynthesis, and that photosystem II and the photosynthesis - antenna proteins pathway played important roles in hormesis. These results provide novel insights into the scientific and safe application of chemical pesticides, and new guidance for investigation into utilizing pesticide hormesis in agriculture. This article is protected by copyright. All rights reserved.

Natural products in crop protection: thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles as antifungal agents and their mechanism of action.

Abstract: BACKGROUND Phytopathogenic fungi can cause a direct loss in economic value of agriculture. Especially Valsa mali Miyabe et Yamada, a devastating phytopathogenic disease especially threatening global apple production, is very difficult to control and manage. To discover new potential antifungal agents, a series of thiosemicarbazone derivatives of 3-acetyl-N-benzylindoles were prepared. Their antifungal activities were first tested against six typically phytopathogenic fungi including Curvularia lunata, Valsa mali, Alternaria alternate, Fusarium graminearum, Botrytis cinerea and Fusarium solani. Then their mechanism of action against V. mali was investigated. RESULTS Derivatives displayed potent antifungal activity against V. mali. Notably, 3-acetyl-N-benzylindole thiosemicarbazone (IV-1: EC50 : 0.59 μg mL-1 ), whose activity was comparable to that of a commercial fungicide carbendazim (EC50 : 0.33 μg mL-1 ), showed greater than 98-fold antifungal activity of the precursor indole. Moreover, compound IV-1 displayed good protective and therapeutic effects on apple Valsa canker disease. By scanning electron microscope (SEM) and RNA-Seq analysis, it was demonstrated that compound IV-1 can destroy the hyphal structure and regulate the homeostasis of metabolism of V. mali via the ergosterol biosynthesis and autophagy pathways. CONCLUSION 3-Acetyl-N-(un)substituted benzylindoles thiosemicarbazones (IV-1~IV-5) can be studied as leads for further structural modification as antifungal agents against V. mali. Particularly, these ergosterol biosynthesis and autophagy pathways can be used as target receptors for design of novel green pesticides for management of congeneric phytopathogenic fungi. This article is protected by copyright. All rights reserved.

Life table analyses for the Tomato Leaf Miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae): effects of plant genotype.

Abstract: BACKGROUND Host plant resistance plays an important role in Integrated Pest Management programs. Crop resistance assessments commonly focus on only single dependent variable, such as larval survival/plant damage, which limits the ability to appreciate the impact of host plants on pest populations in a full sense. Therefore, we performed life table analyses for tomato leaf miner Tuta absoluta, on nineteen Solanum lycopersicum genotypes and a wild Solanum habrochaites accession. These analyses assess the ability of pest to attain high population density on different tomato genotypes. Based on the resulted ranking of tomato resistance at vegetative-stage (45 days old plants), we tested the resistance of six selected genotypes at reproductive-stage (4 months old plants). RESULTS T. absoluta performance was significantly inferior on vegetative-stage of S. habrochaites plants (LA-1777); time taken for the 1st instars to mine the leaves (5±0.14 days), developmental time of early and late stage larvae (8.8±0.2 and 4.2±0.2 days, respectively), pupal period (11.2±0.58 days), and total developmental time (29.4±0.83 days) were significantly longer, and fecundity was significantly lower (18.66±7.24 days), and also recorded highest total mortality (63.33%) as compared to other genotypes resulting in lowest net reproductive rate (R0 ) (11.20±2.51). For the six selected genotypes, the ranking of plant resistance did not change between plants at vegetative and reproductive-stages. CONCLUSION This study suggested that out of 20 screened tomato genotypes, LA-1777 and EC-620343 are the least suitable hosts for T. absoluta to establish fast-growing populations, and thus can be employed in integrated T. absoluta management. This article is protected by copyright. All rights reserved.

Broad host range pathogens as bioherbicides: managing non-target plant disease risk.

Abstract: Plant pathogens with a broad host range are commercially more attractive as microbial bioherbicides than strictly host-specific pathogens due to the wider market potential of a product capable of controlling multiple species. However, the perceived spatiotemporal disease risk to non-target plants is a barrier to their adoption for weed control. We consider two approaches to managing this risk. First, we consider safety zones and withholding periods for bioherbicide treatment sites. These must ensure inoculum spreading from, or surviving at the site, exposes non-target plants to no more inoculum than from natural sources. They can be determined using simple dispersal models and we show that a ratio of added:natural inoculum of 1.0 is biologically reasonable as an "acceptable risk" and a sound basis for safety zones and withholding periods. These would be analogous to the 'conditions of use' for synthetic chemical herbicides aimed at minimising collateral damage to susceptible plants from spray drift and persistent soil residues. Second, weed-specific isolates of broad host range pathogens may avoid the need for safety zones and withholding periods. Such isolates have been found in many broad host range pathogen species. Their utilisation as bioherbicides may more easily meet the requirements of regulators. Mixtures of different weed-specific isolates of a pathogen could provide bioherbicides with commercially attractive spectrums of weed control activity. This article is protected by copyright. All rights reserved.

Biological Control of Weeds in Turfgrass: Opportunities and Misconceptions.

Abstract: Turfgrass systems may offer opportunities for overcoming some constraints on the successful implementation of weed biocontrol. Of the roughly 16.4 million ha of turfgrass in the USA, about 60% to 75% are in residential lawns and 3% are golf turf. Annual expenditures for a standard herbicide treatment regimen for residential turf are estimated to be about $US326 ha-1 , about two to three times that of USA corn and soybean growers. Expenditures can be over $US3000 ha-1 for control of certain weeds like Poa annua in high-value areas like golf fairways or greens, but those applications are made to far smaller areas. Regulatory actions and consumer preferences are creating market opportunities for alternatives to synthetic herbicides in both commercial and consumer markets, but the size of these markets and willingness-to-pay are poorly documented. Turfgrass sites are intensively managed, yet despite the ability to modify site conditions through irrigation, mowing and fertility management, microbial biocontrol agents tested thus far have not provided consistently high levels of weed control expected in the market. Recent advances with microbial bioherbicide products may offer a path to overcome many of the obstacles to success. No single herbicide will control the diversity of turfgrass weeds, nor will any single biocontrol agent or biopesticide. Successful development of weed biocontrol for turfgrass systems will require numerous, effective biocontrol agents for the many weed species found in turfgrass environments, as well as a deeper understanding of different turfgrass market segments, and weed management expectations for each segment. This article is protected by copyright. All rights reserved.

Design, synthesis, crystal structure, and antimicrobial activities of new quinazoline derivatives containing both the sulfonate ester and piperidinylamide moieties.

Abstract: BACKGROUND To discover more efficient antimicrobial agents in agriculture, a series of new quinazoline derivatives bearing both sulfonate ester and piperidine-4-carboxamide moieties were synthesized and assessed for their antimicrobial effects. RESULTS All of the target compounds were fully characterized by 1 H NMR , 13 C NMR, and high-resolution mass spectra, and compound III-6 containing a 3-bromophenyl substituent was clearly confirmed via single-crystal X-ray diffraction analysis. The bioassay results indicated that some compounds displayed noticeable inhibitory effects in vitro against Xanthomonas oryzae pv. oryzicola (Xoc). Further measurements of EC50 values showed that compound III-17 bearing a 4-methoxyphenyl group had the best anti-Xoc efficacy (EC50 = 12.4 μg/mL), far better than the commercialized Bismerthiazol (77.5 μg/mL). Moreover, this compound also demonstrated good protection and curative activities in vivo against rice bacterial leaf streak caused by Xoc. CONCLUSION Compound III-17 had a good potential for further development as a new bactericide for controlling Xoc.

Efficacy of entomopathogenic fungi, nematodes and spinetoram combinations for integrated management of Thrips tabaci: a two-year onion field study.

Abstract: BACKGROUND Two consecutive field trials using a blend of entomopathogens in combination with a new chemistry insecticide were conducted to determine treatment effects on onion thrips (Thrips tabaci Lindeman) populations, crop damage, plant development, crop yield and impact on natural enemies. Products were tested in an onion cropping system and included the insect pathogenic fungus Beauveria bassiana (isolate WG-11), an entomopathogenic nematode Heterorhabditis bacteriophora (strain VS) and the new-chemistry chemical insecticide spinetoram. RESULTS In all treatments, a significant decrease in thrips per plant population was detected in both trials. Overall, dual application of entomopathogens and insecticide was more effective than singly applied treatments. The lowest number of thrips larvae (1.96 and 3.85) and adults (0.00 and 0.00) were recorded when treated with dual application of B. bassiana and spinetoram at 7 day of post application (DPA) after the second spray application in 2017and 2018, respectively. Damage on onion plants was considerably decreased in all treatments relative to the control. The lowest damage was observed on onion plants treated with B. bassiana + spinetoram at 7 DPA after the second spray application during both years. Significant decrease in number of natural enemies (beetles, spiders, mites, lacewings, ants and bugs) on onion plants was recorded during both years. Insect pathogens when applied alone and in combination with each other considerably protected arthropod natural enemies compared to insecticide application applied alone. Significant increase in plant agronomic traits was observed compared to the control. Among all the treatments, B. bassiana + spinetoram produced maximum leaf length, leaf weight, total leaves, neck diameter, bulb diameter, number of rings per bulb, bulb weight, dry matter and plant yield following the 2017and 2018 applications, respectively. CONCLUSION The findings of study reveal the potential of using insect pathogens and insecticide for control of T. tabaci. However, combinations containing spinetoram are harmful to non-target organisms, whereas biological control agents help in protecting biodiversity in onion agroecosystems. This article is protected by copyright. All rights reserved.

A microbial bioherbicide for Striga hermonthica control: production, development, and effectiveness of a seed coating agent.

Abstract: Witchweed (Striga hermonthica), also called striga, is a parasitic weed that causes high yield losses in maize on more than 200,000 ha in Kenya alone. A new commercial, biological herbicide developed in Kenya is able to control striga effectively. The product was approved for use by the Pest Control Products Board in Kenya in September, 2021. It is self-produced in villages using a secondary inoculum provided by a commercial company. The formulated product has some disadvantages, which are a complicated production process, a very short shelf life and high application rate. Additionally, the product has to be applied manually and therefore can only be used in manual production, leaving out the opportunity for farmers using mechanization. For this reason, efforts have been made to formulate the active ingredient Fusarium oxysporum f. sp. strigae strain DSM 33471, as a powder and to use it as a seed coating agent. This article deals with the production of the Fusarium spore powder, its properties, its application to the seed, and its herbicidal effect demonstrated in the first two field trials. The F. oxysporum strain was originally isolated from a wilting striga plant in Kenya. The strain was virulence enhanced to over produce the amino acids leucine, methionine and tyrosine. These amino acids are responsible for a second mode of action apart from the wilting causing effect of the fungus on striga. Whereas, leucine and tyrosine have a herbicidal effect, ethylene from methionine triggers the germination of striga seeds in the soil. Additionally, the strain has been improved to be resistant to the fungicide captan, which is commonly used to treat maize seed in Kenya. Seed coating tests conducted on 25 striga-infested small holder farms spread out in six counties of western Kenya reported yield increases of up to 88 %. A second trial carried out by the Kenyan Agricultural and Livestock Research Organization showed a 93% reduction of emerged striga plants. This article is protected by copyright. All rights reserved.

When a plant invader meets its old enemy abroad: what can be learnt from accidental introductions of biological control agents.

Abstract: Accidental introductions of biological weed control (BWC) agents (i) offer opportunities to assess host use of agents with a potentially broader fundamental host-range than those approved for field release directly in target areas; (ii) urge national authorities to rapidly respond as they may threaten native species or crops, and by this (iii) help advancing post-release studies, a neglected aspect of BWC. Through detailed insights gained from studying the recent accidental introduction of the ragweed leaf beetle Ophraella communa into Europe, we derive suggestions for overcoming barriers to adoption of BWC by re-evaluating the predictive power of pre-release studies and, thus, the presently strict criteria for deciding upon their release that might exclude safe and efficient agents. By using the allergenic weed Ambrosia artemisiifolia and the accidentally introduced BWC agent O. communa as study system, we also hope to raise the awareness of authorities to consider biological control more prominently as a key approach for pest management in the "One Health" concept, which aims to sustainably balance and optimize the health of people, animals, plants and ecosystems. This article is protected by copyright. All rights reserved.

Modelling the factors affecting the spatiotemporal distribution of cabbage stem flea beetle (Psylliodes chrysocephala) larvae in winter oilseed rape (Brassica napus) in the UK.

Abstract: BACKGROUND Cabbage stem flea beetle (CSFB; Psylliodes chrysocephala L.) management in oilseed rape (Brassica napus L.) has become an urgent issue in the absence of permitted and effective insecticides. Understanding the meteorological and management factors affecting their population dynamics has become critical to the development of pest management strategies. RESULTS The spatio-temporal changes in CSFB larval populations were assessed both in autumn and spring, in the UK from 2003 to 2017 (a period encompassing pre-and post-neonicotinoid insecticide restriction).. After the neonicotinoid ban in 2013, the number of larvae both in autumn and spring increased 10-fold in the UK. When neonicotinoids were available, later sown crops contained fewer larvae than early sown crops, and bigger fields had fewer larvae than smaller fields, whereas after the ban, bigger fields tended to have more larvae than smaller fields. Wet and mild/hot Septembers were related with higher numbers of larvae when neonicotinoids were available and with lower larval numbers after the neonicotinoid ban. Low temperatures in December and January combined with high rainfall were related with high numbers of larvae in spring both before and after the neonicotinoid ban. CONCLUSION This study will help to produce decision support systems that allow future predictions of regional CSFB population changes and will help growers and consultants to adjust their management methods to reduce the risk of high infestations. This article is protected by copyright. All rights reserved.

Effect of yhfS gene on Bt LLP29 antioxidant and UV rays resistance.

Abstract: BACKGROUND Bacillus thuringiensis (Bt) is a kind of widely used microbial insecticide. However, its persistence is limited because of ultraviolet rays or other environmental factors. The yhfS gene, which encodes acetyl-CoA acyltransferase, plays an important role in lipid transport and metabolism in many organisms. To explore whether it is related to the stress resistance of Bt LLP29, the yhfS gene knockout strain LLP29 Δ-yhfS and the complementary strain LLP29 R-yhfS were generated successfully by homologous recombination technology, and the related phenotypic changes were compared in this study. RESULTS Gene yhfS was found functional on anti-ultraviolet radiation in Bt by comparing the anti-ultraviolet radiation ability of Bt LLP29 harboring yhfS or not. Enzyme activity assay of key enzymes showed the EMP pathway was enhanced and the TCA cycle as well as butanoate synthesis were repressed when the gene was deleted. At the same time, the amino acid content were decreased but NADH and ROS content were increased. Most noteworthy, the antioxidases (such as SOD and POD) activities and some potent antioxidants (such as pyruvate, carotenoids and NADPH) content of LLP29 Δ-yhfS were lower than those of LLP29. CONCLUSION These tests revealed that the loss of yhfS gene led to metabolic disorders and the reduction of antioxidant ability of Bt. Higher ROS level and lower anti-oxidative capacity might be responsible for the reduced UV resistance when the gene was deleted. These results not only greatly enrich mechanism of Bt UV resistance, but also provide important theoretical basis for Bt application. This article is protected by copyright. All rights reserved.

Insecticide resistance monitoring of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) and its mechanism to chlorantraniliprole.

Abstract: BACKGROUND The rice leaffolder, Cnaphalocrocis medinalis (Guenée), has become an increasingly occurring pest in Asia in recent years. Chemical control remains the most efficient and primary tool for controlling this pest. In this study, we report the resistance status of C. medinalis in China to multiple insecticides including chlorantraniliprole and the main resistance mechanism. RESULTS Significant variations among field populations of C. medinalis in their resistance to ten insecticides were observed during 2019-2022. Most of the tested field populations have developed low to moderate levels of resistance to abamectin (RR = 2.4-22.2), emamectin benzoate (RR = 1.9-40.3) and spinetoram (RR = 4.2-24.8). Some field populations have developed low resistance to chlorpyrifos (RR = 0.9-6.8). Indoxacarb, metaflumizone, methoxenozide and Bt potency against all tested populations remained similar. For diamides, significantly higher levels of resistance to chlorantraniliprole (RR = 64.9-113.7) were observed in 2022, whereas all tested field populations in 2019-2021 exhibited susceptible or moderate resistance level to chlorantraniliprole (RR = 1.3-22.1). Cross resistance between chlorantraniliprole and tetraniliprole was significant. Analysis of ryanodine receptor (RyR) mutations showed that mutation of I4712M was present in resistant populations of C. medinalis with different levels of chlorantraniliprole resistance and was the main mechanism conferring diamide resistance. Mutation of Y4621D was also detected in one tested population. Resistance management strategies for the control of C. medinalis are discussed. CONCLUSION C. medinalis has developed high level of resistance to chlorantraniliprole. RyR mutations were deemed as the mechanism. This article is protected by copyright. All rights reserved.

Evaluation of a Guardian Plant System to Suppress Frankliniella occidentalis (Thysanoptera: Thripidae) in Greenhouse Ornamentals.

Abstract: BACKGROUND Western flower thrips (WFT), Franklinella occidentalis (Pergande), is an economically damaging pest of greenhouse ornamentals. A 'guardian plant system' (GPS) that targeted WFT was evaluated under controlled and commercial greenhouse conditions. This system used mycotized millet grains with the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin applied to soil of potted marigolds, Tagetes patula (L.), combined with the foliar-dwelling predatory mite Neoseiulus (=Amblyseius) cucumeris (Oudemans) in slow-release sachets under controlled greenhouse conditions, and with the addition of a pheromone lure under commercial settings. RESULTS Significantly fewer WFT and less foliar damage on GPS was observed over the 10- and 12-week experimental periods compared to the untreated controls. Predatory mites were maintained up to 10 weeks with one release under controlled greenhouse conditions and 12 weeks with two releases in commercial greenhouses. In commercial greenhouses, greater numbers of WFT were found on marigolds than on crop plants within 1 meter of the system. Fungal granules persisted for 12 weeks up to 2.5 × 105 CFU/g in the GPS soil. CONCLUSION The use of biological control agents to suppress WFT within a GPS could be a useful IPM strategy for greenhouse production. The marigold GPS attracted WFT which were suppressed primarily through predation by foliar-dwelling predatory mites and to a lesser extent, infection from conidia produced by the granular fungal formulation in the soil. Further investigations into system deployment and fungal granular application rates and new fungal formulations are suggested to improve system efficacy.